Multi-stage turbine rotor



Jan. 3, 1967 B. c. HALL, JR 3,295,825

MULTI STAGE TURBINE ROTOR Filed March 10, 1965 I N VEN'TOR.

zaz 6 m 1r 62' 2f 72 6'6 ATTORNEY United States Patent 3,295,825MULTI-STAGE TURBINE ROTOR Beuford C. Hall, Jr., Indianapolis, Ind.,assignor to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Filed Mar. 10, 1965, Ser. No. 438,476 7 Claims. (Cl. 253-77)This invention relates generally to a multi-stage turbine rotor and morespecifically to a multi-stage turbine rotor having an annular spacerdisposed 'between successive stages thereof.

It is common practice to utilize turbine rotors comprising a rotor wheelhaving axial circumferentially spaced slots in which are mounted theroots of a plurality of radially extending turbine blades. Obviously, inthis type of construction some means must be provided for preventing theblade roots from sliding out of the slots. It is also common to providean annular spacer between successive stages in a multi-stage turbinerotor.

The turbine section of a gas turbine engine is subjected to thermaltransients in its normal operation. These terminal transients inducethermal stresses in the parts located therein. Any rotating annular partin the turbine section, such as a spacer, is also subjected tocentrifugal forces which produce free ring'hoop stresses in the part.The stress resulting from these two sources is of a transient naturevarying in magnitude and sense, i.e., compressive to tensile tocompressive, etc. This transient type of stress fatigues the part,causing premature failure. Segmenting the spacer overcomes the stressfatigue problem since it no longer carries hoop stress and the thermallyinduced circumferential expansion stresses. However, in order to providefor suflicient circumferential growth, other problems may arise such asproviding radial flow paths through the spacer or providing a rotatingbody having shiftable weights which may become unbalanced and produceundesirable vibrations. I

It is, therefore, an object of this invention to provide a multistageturbine rotor having an annular spacer disposed between successivestages which will not prematurely fatigue.

Another object is to provide a multi-stage turbine rotor having anannular spacer disposed between successive stages which is segmented toeliminate the stresses therein to provide a longer life.

Another object is to provide a multi-stage turbine rotor having anannular segmented spacer which remains balanced at all times and underall conditions.

Another object is to provide a multi-stage turbine rotor having asegmented annular spacer which will not produce undesirable vibrations.

Another object is to provide a multi-stage turbine rotor having asegmented annular spacer which minimizes radial flow therethrough.

Another object is to provide a multi-stage turbine rotor having stagescomprising separable blades retained in mounting slots in a rotor with asegmented spacer between successive stages.

Another object is to provide a multi-stage turbine rotor having asegmented spacer disposed between successive stages and means topositively locate segments and retain the separable blades in the rotormounting slots to eliminate parts and provide a relatively simpledevice.

The exact nature of this invention as well as other objects andadvantages thereof will be readily apparent from consideration of thefollowing specification relating to the annexed drawings in which:

FIGURE 1 is a transverse section of a gas turbine engine showing twostages of a multi-stage turbine rotor in accordance with the presentinvention.

Patented Jan. 3, 1967 FIGURE 2 is a section taken along the line 2-2 ofFIGURE 1 and looking in the direction of the arrows.

FIGURE 3 is a section taken along the line 33 of FIGURE 1 and looking inthe direction of the arrows.

FIGURE 4 is a section taken along the line 44 of FIGURE 1 and looking inthe direction of the arrows.

FIGURE 5 is a section taken along the line 5-5 of FIGURE 4 and lookingin the direction of the arrows.

FIGURE 1 shows two stages of a multi-stage turbine rotor for a gasturbine engine. The turbine rotor is rotatably mounted in a casing 12with a guide vane ring 14 mounted between the axially spaced stages 16and 18. The guide vane ring 14 comprises an outer shroud 20 which clampsa liner 22 within the forward portion of the casing 12, a plurality ofradially inwardly extending guide vanes 24 and an inner shroud band 26which connects the inner ends of the vanes 24. The front stage 16comprises a rotor wheel 28 having a plurality of axial slots 30 spacedabout its rim as can best be seen in FIGURE 3. The slots are ofconventional fir tree cross-section and receive the fir tree roots 32 ofa plurality of blades 34. Spaced radially outwardly from the root 32 bystalk 40 is a hollow platform 42. The stalks 40 are provided withcircumferentially extending ears 44 which, together with the platforms42, form chambers 46 which house vibration dampers Returning to FIGURE1, it can be seen that the roots 32 have L-shaped forward and rearwardtangs 36 and 38, respectively, extending axially therefrom. An annularfront side plate 50 abuts the leading edge wall 52 of the front rotorwheel 28 with the forward tangs'36 extending through slots 54 therein.The outer edge of plate 50 rests in a groove 56 in the underside ofplatform 42 and an annular flange 58 adjacent the inner edge abutsshoulder 60 on the wheel 28 positioning the plate 50 on wheel 60. Theportions 55 of the side plate 50 lying just inwardly of the slots 4 aredisposed between the axial legs on the forward tangs 36 and the leadingedge wall 52 and thus prevent the roots 32 from being withdrawn axiallyrearwardly from the slots 30. A frontal view of the plate 50 is shown inFIGURE 2.

A rear side plate 62 abuts the trailing edge wall 64 of front rotorwheel 28 with the rear tangs 36 extending through bayonet slots 66therein. An annular flange 78 is provided on the inner circumferentialedge of the back side plate 72 to engage the shoulder on the front rotorwheel 28 to mount the plate 72 thereon. A second flange 82 is locatedradially outwardly from the flange 78. The bayonet slots 66 which canbest be seen in FIGURE 4 have right-hand portions 68 substantiallyradially coextensive with the rear tangs 36 and left-hand portions 70which are somewhat smaller. After the rear side plate 62 has beenthreaded onto the rear tangs into abutment with the wheel 28, it isrotatably indexed slightly clockwise. Retaining edges 72 on the rearplate 62 now occupy the spaces between the axial legs of the L-shapedtangs 36 and rotor wheel 28 to prevent the roots 32 from being withdrawnaxially forwardly from slots 54. The rear side plate 62 has a pluralityof pilot apertures 76 which will align with a corresponding number ofpilot cavities 74 in rotor wheel 28 when the rear side plate 62 is inits interlocking position. Flange 82, pilot cavities 74 and apertures 76have a function to be described later.

The rotor wheel 28 has a cylindrical extension 84 pro vided with facesplines 86 which mesh with splines 88 on a cylindrical extension 90 onthe rear turbine stage 18. The parts of the rear stage 18 aresubstantially identical to those of the front stage and carry primedidentifying numerals which are the same as the unprimed numerals used inthe first stage. However, the following modifications are present: thefront side plate 50' has an annular flange 92' adjacent its outercircumferential edge, the

3 platform 42' is not hollow, and the tips of the blades 34' areconnected by a shroud ring 94.

An annular spacer generally indicated at 96 is provided between thefront stage 16 and the rear stage 18. This annular spacer 96 comprises aplurality of arcuate spacer segments 98, as can best be seen in FIGURE4. The circumferential edge walls 100 are grooved at 102 forming spacedtongues 104. The tongues on the right-hand walls are displaced fromthose on the left-handwalls so that adjacent segments 98 will interfitthe tongues on one segment being received in the grooves on the adjacentsegment and vice-versa. This interfit allows for suflicient radialgrowth without providing a path for radial flow through the shroud. Theleading and trailing edge walls of the spacer segments 98 have arcuatemounting grooves 106 and 108 respectively. The grooves 106 and 108respectively receive the annular flange 82 on the front stage andannular flange 92 on the rear stage 18 to support each segment 98 as asimple beam. The outer surface of the spacers 96 have spaced flutedportions 110 which cooperate with spaced annular lands 112 on the innershroud band 26 to form a labyrinth seal. Each spacer segment is alsoprovided with a depending pilot tlug 114 which extends centrally fromits leading edge. The pilot lug 114 extends through the aperture 76 inthe rear side plate 72 and into. pilotcavity 74 in the rotor wheel 28.Thus the lug serves to locate the individual segment 96 as well as'r'estrains the rear side plate 62 from rotatable movement and retainsit in its interlocking position where edge 72 interferes with the axiallegs on the rear tangs 38. When all of the segments 98 are mounted onthe flanges '82 and 92', they will form an annular spacer 96. The spacer96 will be segmented with the ends of the segments 98 abutting to permitradial and circumferential thermal growth without stress transfer andoverlapping to reduce radial flow therethrough. Each individual spacersegment will be positively located to prevent shifting and unbalance andvibration. The segments cooperate with the wheel 28 to retain the rearside plate 62 indexed at its interlocked position wherein the blades 34are locked to the rotor wheel 28 to form the front stage 16.

, Thus it can be seen that I haveprovided a multi-stage turbine rotorhaving a segmented annular spacer between successive stages wherein eachof the segments of the annular spacer is positively located so as toretain the radially extending blades mounted to the rotor to eliminateparts and provide a simple device while attaining all of theabove-mentioned objects.

It should be understood, of course, that the foregoing i disclosurerelates only to a preferred embodiment of the invention and thatmodifications or alterations may be made therein without departing fromthe spirit and scope of the invention set forth in the appended claims.

I claim: t 1. In a multi-stage bladed rotor, the combination comprising:

a first rotor wheel having a plurality of circumferentially spaced axialslots, a plurality of radially extending blades having roots 'mounted insaid slots, I first and second tangs on said roots, means engaging saidfirst tangs to prevent said blades from being withdrawn axially in onedirection from said first wheel, i an annular side plate having aplurality of bayonet slots abutting the edge wall of said firs-t wheeland said roots with said second tangs extending through said slots, saidside plate being indexable to an interlocking poistion to engage saidsecond tangs and prevent said blades from being withdrawn axially in theopposite direction from said first wheel, 1 a plurality of spacersegments mounted at one end to said side wall, said segments abuttingadjacent segments to form an annular spacer,

a plurality of radially extending blades having roots I mounted in saidslots,

means to prevent said blades from being withdrawn axially from saidfirst wheel in a first direction,

tangs extending from the end wall of said roots, in said firs-tdirection,

an annular side plate having a plurality of bayonet slots abutting theend wall of said first wheel and said roots with said tangs extendingthrough said slots, said side plate being rotatable to an interlockingposition to engage said tangs and prevent said blades from beingwithdrawn axially in an opposite direction from said first wheel,

a plurality of spacer segments mounted at one end to said sidewall, saidsegments abutting adjacent segments to form an annular spacer,

pilot means on said segments engaging said side plate and said firstwheel to locate said segments and to I retain said side plate in saidinterlocking position,

and

a second bladed rotor wheel spaced axially from and connected to saidfirst wheel, said second wheel including means to mount the opposite endof said spacer segments thereon.

3. In a multi-stage bladed rotor, the combination comprising:

a first rotor wheel having a plurality of axial slots spaced about itscircumference and a plurality of pilot cavities in its end wall,

a plurality of radially extending blades having roots mounted in saidslots,

I means to prevent said blades from being Withdrawn axially in onedirection from said first wheel,

tangs extending axially from said roots in said one direction, 1

an annular side plate having a plurality of bayonet slots and aplurality of pilot apertures, said plate abutting the end wall of saidfirst wheel and said roots with said tangs extending through said slots,said side plate also being indexable to an interlocking position whereinsaid tangs are engaged to prevent said blades from being withdrawnaxially from said first wheel in an opposite direction and wherein saidpilot apertures are aligned with said pilot cavities,

a plurality of spacer segments mounted at one end to said side wall,said segments abutting adjacent segments to form an annular spacer,

pilot means on said segments extending into said aligned pilot aperturesand cavities to locate said segments and to retain said side plate insaid interlocking position, and

a second bladed rotor wheel spaced axially from and connected to saidfirst'wheel, said second wheel including means to mount the opposite endof said spacer segments thereon.

4. In a multi-stage bladed rotor, the combination com prising: A

a first rotor wheel having a plurality of axial slots spaced about itscircumference and a plurality of pilot cavi- I means to prevent saidblades from being withdrawn axially in one direction from said firstwheel,

tangs extending axially from said roots in said one direction,

an annular side plate having a plurality of bayonet slots and aplurality of pilot apertures abutting the end wall-of said first wheelwith said tangs extending through said slots, said side plate beingindexable to an interlocking position wherein said tangs are engaged toprevent said blades from being withdrawn axially in an oppositedirection from said first wheel and wherein said pilot apertures arealigned with said pilot cavities,

an annular flange extending axially from said side plate in said onedirection,

plurality of arcuate spacer segments having arcuate grooves in their endWall, said segments abutting adjacent segments to form an annular spacerwith an annular groove which receives said flange to support said spaceron said side wall,

depending pilot lug on each segment extending into said aligned pilotapertures and cavities to locate said segment and to retain said sideplate in said interlocking position, and

second bladed rotor wheel spaced axially from and connected to saidfirst wheel, said second wheel including means to mount the opposite endof said spacer segments thereon.

In a multi-stage bladed rotor, the combination comprising:

a first rotor wheel having a plurality of axial slots spaced about itscircumference and a plurality of pilot cavities in its trailing edgeWall,

plurality of radially extending blades having roots mounted in saidslots,

front and rear tangs on said roots, means engaging said front tangs toprevent said blades from being withdrawn axially rearwardly from saidfirst wheel,

an annular side plate having a plurality of bayonet slots and aplurality of pilot apertures abutting the trailing edge wall of saidfirst wheel with said rear tan-gs extending through said slots, saidside plate being indexable to an interlocking position wherein said reartangs are engaged to prevent said plates from being withdrawn 'axiallyforwardly from said first wheel and wherein said pilot apertures arealigned with said pilot cavities,

an annular flange extending radially from said side plate, plurality ofarcuate spacer segments having arcuate grooves in their leading andtrailing edge walls,

grooves in their one side wall and tongues on their opan annular flangeextending forwardly from said second wheel, and

an annular groove in the trailing edge wall of said spacer, said annulargroove receiving said annular flange to support the opposite end of saidspacer.

6. In a multi-stage bladed rotor, the combination comprising:

a first rotor wheel having radially extending blades with roots mountedin circumferentially spaced axial slots,

means to prevent said blades from being withdrawn axially from saidfirst wheel in a first direction,

further means mounted on said rotor so as to be circumferentiallyindexable between a first and second position, said further meanspermitting axial withdrawal of said blades in an opposite direction whensaid further means is in said first position and preventing axialwithdrawal of said blades in said opposite direction when said furthermeans is in said second position,

a plurality of spacer segments mounted at one end to said first 'wheel,said segments abutting adjacent segments to form an annular spacer,

pilot means on said segments to locate said segments with respect tosaid first wheel and to retain said further means in said secondposition, and

a second bladed rotor wheel spaced axially from and connected to saidfirst wheel, said spacer segments mounted at their opposite end to saidsecond wheel.

7. In a multi-stage bladed rotor, the combination comprising:

a first rotor wheel having a plurality of circumferentially axial slots,

a plurality of radially extending blades having roots mounted in saidslots,

means to prevent said blades from being withdrawn axially from saidfirst wheel in a first direction,

tangs extending from the end wall of said roots in said first direction,

an annular side plate having a plurality of bayonet slots abutting theend wall of said first wheel and said roots with said tangs extendingthrough said 'slots, said side plate being rotatable to an interlockingposition to engage said tangs and prevent said blades from beingwithdrawn axially in an opposite direction from said first Wheel,

an annular spacer mounted at one end to said side wall,

pilot means on said spacer engaging said side plate and said first wheelto retain said side plate in said interlocking position, and

a second bladed rotor wheel spaced axially from and connected to saidfirst wheel, said second wheel including means to mount the opposite endof said spacer thereon.

References Cited by the Examiner UNITED STATES PATENTS 2,689,682 9/1954Boyd et al 230-134 2,755,063 7/1956 Wilkinson 25377 2,985,426 5/1961Hunter et al 25377 X 2,998,959 9/1961 Haworth et al 253-77 3,010,69611/1961 Everett 253-77 MARTIN P. SCHWADRON, Primary Examiner,

EVERETTE A. POWELL, JR., Examiner.

1. IN A MULTI-STAGE BLADED ROTOR, THE COMBINATION COMPRISING: A FIRSTROTOR WHEEL HAVING A PLURALITY OF CIRCUMFERENTIALLY SPACED AXIAL SLOTS,A PLURALITY OF RADIALLY EXTENDING BLADES HAVING ROOTS MOUNTED IN SAIDSLOTS, FIRST AND SECOND TANGS ON SAID ROOTS, MEANS ENGAGING SAID FIRSTTANGS TO PREVENT SAID BLADES FROM BEING WITHDRAWN AXIALLY IN ONEDIRECTION FROM SAID FIRST WHEEL, AN ANNULAR SIDE PLATE HAVING APLURALITY OF BAYONET SLOTS ABUTTING THE EDGE WALL OF SAID FIRST WHEELAND SAID ROOTS WITH SAID SECOND TANGS EXTENDING THROUGH SAID SLOTS, SAIDSIDE PLATE BEING INDEXABLE TO AN INTERLOCKING POSITION TO ENGAGE SAIDSECOND TANGS AND PREVENT SAID BLADES FROM BEING WITHDRAWN AXIALLY IN THEOPPOSITE DIRECTION FROM SAID FIRST WHEEL, A PLURALITY OF SPACER SEGMENTSMOUNTED AT ONE END TO SAID SIDE WALL, SAID SEGMENTS ABUTTING ADJACENTSEGMENTS TO FORM AN ANNULAR SPACER, PILOT MEANS ON SAID SEGMENTSENGAGING SAID SIDE PLATE AND SAID FIRST WHEEL TO LOCATE SAID SEGMENTSAND TO RETAIN SAID SIDE PLATE IN SAID INTERLOCKING POSITION, AND ASECOND BLADED ROTOR WHEEL SPACED AXIALLY FROM AND CONNECTED TO SAIDFIRST WHEEL, SAID SECOND WHEEL INCLUDING MEANS TO MOUNT THE OPPOSITE ENDOF SAID SPACER SEGMENTS THEREON.